Semiconductor light-emitting device, electrode for the device, method for fabricating the electrode, LED lamp using the device, and light source using the LED lamp

ABSTRACT

A semiconductor light-emitting device includes a semiconductor substrate that has a rear surface formed with a first electrode, a semiconductor layer that includes a light-emitting portion and is formed on the semiconductor substrate, a plurality of dispersed electrodes that are individually formed on a part of the surface of the semiconductor layer to make ohmic contact with the semiconductor layer, a transparent conductive film that covers the surface of the semiconductor layer and the dispersed electrodes to electrically conduct with the dispersed electrodes, and a pad electrode that is formed on a part of the surface of the transparent conductive film to electrically conduct with the transparent conductive film.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. §111(a)claiming benefit pursuant to 35 U.S.C. §119(e)(1) of the filing date ofthe Provisional Application Ser. No. 60/164,861 filed Nov. 12, 1999pursuant to 35 U.S.C. §111(b).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light-emitting devicethat emits light in the green color to red-color bands, an electrode forthe semiconductor light-emitting device, a fabrication method of theelectrode, an LED lamp using the semiconductor light-emitting device,and a light source using the LED lamp.

2. Description of the Prior Art

As light-emitting devices such as a light-emitting diode (LED) and alaser diode (LD) which emit light in the reddish-orange band, alight-emitting device including a light-emitting portion structureformed of a mixed crystal layer of (Al_(X)Ga_(1−Y))_(y)In_(1−Y)P(0≦X≦1,0<Y<1) has heretofore been known, for example, in JP-A HEI8(1996)-83927. The light-emitting device disclosed in this publicationof the unexamined application is constructed in such a manner that atransparent conductive film made of indium tin oxide is stacked on thesurface of the light-emitting portion made of the mixed crystal layer of(Al_(X)Ga_(1−X))_(Y)In_(1−Y)P and that an upper plane electrode isformed on the transparent conductive film. With this structure, currentfrom the upper plane electrode is diffused to a region as wide aspossible on the surface of the light-emitting portion via thetransparent conductive film.

However, in the conventional light-emitting device, ohmic contactbetween the transparent conductive film and the surface of thelight-emitting portion cannot be achieved sufficiently, and this is amain cause to increase a forward current and degrade service lifecharacteristics. In order to improve this point, a window layer of JP-AHEI 11(1999)-17220, for example, is formed on the surface of alight-emitting potion, and a contact layer is formed on this windowlayer. Furthermore, a transparent conductive film (a conductivetransparent oxide layer) made of indium tin oxide is stacked on thecontact layer, and an upper plane electrode (an upper layer electrode)on the transparent conductive film, thus constituting a light-emittingdevice. Thus, a current from this upper plane electrode is diffused to aregion as wide as possible on the surface of the light-emitting portionvia the transparent conductive film, contact layer and window layer.

In the light-emitting device disclosed in JP-A HEI 11(1999)-17220,however, though the ohmic contact between the transparent conductivefilm and the semiconductor layer is improved, since the contact layer isprovided, emitted light is absorbed by this contact layer. Accordingly,a high luminance light emission cannot be sufficiently achieved, and alight-emitting efficiency is not improved.

The present invention has been proposed considering the aforementionedproblem. An object of the present invention is to provide asemiconductor light-emitting device which is capable of realizing a goodohmic contact between an electrode and a semiconductor layer andsignificantly improving a light-emitting efficiency without absorptionof emitted light, an electrode for the semiconductor light-emittingdevice, an LED lamp using the semiconductor light-emitting device, and alight source using the LED lamp.

SUMMARY OF THE INVENTION

To achieve the above object, the present invention provides asemiconductor light-emitting device which comprises: a semiconductorsubstrate having a rear surface on which a first electrode is formed; asemiconductor layer including a light emitting portion, that is formedon the semiconductor substrate; dispersed electrodes formed individuallyon a part of a surface of the semiconductor layer and making ohmiccontact with the semiconductor layer; a transparent conductive filmformed so as to cover the surface of the semiconductor layer and thedispersed electrodes, the transparent conductive film electricallyconducting with the dispersed electrodes; and a pad electrode formed ona part of a surface of the transparent conductive film, the padelectrode electrically conducting with the transparent conductive film.

The semiconductor light-emitting device of the invention induces aconfiguration in which the dispersed electrodes are formed on thesemiconductor layer surface around the pad electrode when viewed fromabove.

The semiconductor light-emitting device of the invention includes aconfiguration in which the dispersed electrodes are formed on thesemiconductor layer surface at portions where the dispersed electrodesdo not overlap the pad electrode when viewed from above.

The semiconductor light-emitting device of the invention includes aconfiguration in which the dispersed electrodes are not formed on thesemiconductor layer surface at portions where the dispersed electrodesoverlap the pad electrode when viewed from above.

The semiconductor light-emitting device of the invention furtherincludes a feature that the total plane area of the dispersed electrodesis smaller than the area of the pad electrode.

The semiconductor light-emitting device of the invention includes afeature that the total plane area of the dispersed electrodes is 3% to30% of the effective light emitting area.

The semiconductor light-emitting device of the invention includes afeature that the light-emitting portion is made of AlGaInP.

The semiconductor light-emitting device of the invention includes afeature that the semiconductor layer is formed by the metal organicchemical vapor deposition (MOCVD).

The semiconductor light-emitting device of the invention includes afeature that the transparent conductive film is made of indium tin oxide(ITO).

The semiconductor light-emitting device of the invention furtherincludes a configuration in which the pad electrode is formed on thesemiconductor layer via the transparent conductive film, but there is notransparent conductive layer on the surface of the pad electrodesubjected to wire-bonding.

The semiconductor light-emitting device of the invention includes aconfiguration in which the pad electrode is formed on the semiconductorlayer surface at the center when viewed from above.

The present invention further provides an electrode for thesemiconductor light-emitting device, which comprises: dispersedelectrodes formed individually on a part of a surface of thesemiconductor layer including a light emitting portion, the dispersedelectrodes making ohmic contact with the semiconductor layer; atransparent conductive film formed so as to cover the surface of thesemiconductor layer and the dispersed electrodes, the transparentconductive film electrically conducting with the dispersed electrodes;and a pad electrode formed on a part of a surface of the transparentconductive film, the pad electrode electrically conducting with thetransparent conductive film.

The electrode of the invention for the semiconductor light-emittingdevice includes a configuration in which the dispersed electrodes areformed on the semiconductor layer surface around the pad electrode whenviewed from above.

The electrode of the invention for the semiconductor light-emittingdevice includes a configuration in which the dispersed electrodes areformed on the semiconductor layer surface at portions where thedispersed electrodes do not overlap the pad electrode when viewed fromabove.

The electrode of the invention for the semiconductor light-emittingdevice further includes a feature that the total plane area of thedispersed electrodes is smaller than the area of the pad electrode.

The electrode of the invention for the semiconductor light-emittingdevice includes a feature that the total plane area of the dispersedelectrodes is 3 to 30% of the effective light emitting area.

The electrode of the invention for the semiconductor light-emittingdevice includes a feature that the transparent conductive film is madeof indium tin oxide.

The electrode of the invention for the semiconductor light-emittingdevice further includes a configuration in which the pad electrode isformed on the semiconductor layer via the transparent conductive film,but there is no transparent conductive layer on the surface of the padelectrode subjected to wire-bonding.

The electrode of the invention for the semiconductor light-emittingdevice includes a configuration in which the pad electrode is formed onthe semiconductor layer surface at the center when viewed from above.

The invention further provides a method for fabricating the electrodefor the semiconductor light-emitting device comprising a first step offorming dispersed electrodes individually on a part of a surface of asemiconductor layer including a light emitting portion, the dispersedelectrodes making ohmic contact with the semiconductor layer; a secondstep of forming a transparent conductive film so as to cover the surfaceof the semiconductor layer and the dispersed electrodes, the transparentconductive film electrically conducting with the dispersed electrodes;and a third step of forming a pad electrode on a part of a surface ofthe transparent conductive film, the pad electrode electricallyconducting with the transparent conductive film.

The electrode fabrication method of the invention includes aconfiguration in which the dispersed electrodes are formed on thesemiconductor layer surface around the pad electrode when viewed fromabove.

The electrode fabrication method of the invention includes aconfiguration in which the dispersed electrodes are formed on thesemiconductor layer surface at portions where the dispersed electrodesdo not overlap the pad electrode when viewed from above.

The electrode fabrication method of the invention includes aconfiguration in which the dispersed electrodes are not formed on thesemiconductor layer surface at portions where the dispersed electrodesoverlap the pad electrode when viewed from above.

The electrode fabrication method of the invention includes a featurethat the transparent conductive film is made of indium tin oxide.

The electrode fabrication method of the invention includes a featurethat the transparent conductive film is formed by a spattering method,and the pad electrode is formed by a vapor deposition method.

The electrode fabrication method of the invention further includes aconfiguration in which the pad electrode is formed on the semiconductorlayer via the transparent conductive film, but there is no transparentconductive layer on the surface of the pad electrode subjected towire-bonding.

The invention further provides an LED lamp using the semiconductorlight-emitting device.

The invention further provides a light source using the LED lamp.

In the present invention, since the dispersed electrodes are formed on apart of the surface of the semiconductor layer, as described above, theelectrical resistance between the semiconductor layer and the dispersedelectrodes is made much smaller than that between the transparentconductive film and the semiconductor layer. Since a major part of adriving current supplied from the pad electrode flows through a pathbetween the semiconductor layer and the dispersed electrodes having asmaller electrical resistance, light can be emitted from thelight-emitting portion around the dispersed electrodes. Furthermore,since the major dispersed electrodes are disposed so as not to overlapthe pad electrode, no light emission toward immediately below the padelectrode occurs. Therefore, a major part of light can be emitted upwardwithout being intercepted by the pad electrode. Thus, the emissionefficiency can be improved to a great extent.

The above and other objects, features and advantages of the presentinvention will become apparent from the description of the preferredembodiments of the invention made herein below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing the configuration of asemiconductor light-emitting device according to the present invention.

FIG. 2 is a cross section taken along line II—II in FIG. 1.

FIG. 3 is a plan view showing the configuration of a first embodiment ofthe semiconductor light-emitting device according to the presentinvention.

FIG. 4 is a cross section taken along line IV—IV in FIG. 3.

FIG. 5 is a plan view showing the configuration of a second embodimentof the semiconductor light-emitting device according to the presentinvention.

FIG. 6 is a cross section taken along line VI—VI in FIG. 5.

FIG. 7 is a plan view showing the configuration of a third embodiment ofthe semiconductor light-emitting device according to the presentinvention.

FIG. 8 is a cross section taken along line VIII—VIII in FIG. 7.

FIG. 9(a) to FIG. 9(y) are plan views each showing the arrangement ofdispersed electrodes according to the present invention.

FIG. 10 is a schematic view showing one embodiment of an LED lamp usinga semiconductor light-emitting device according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in detail hereinbelow with reference to the accompanying drawings.

FIGS. 1 and 2 are schematic views showing the configuration of asemiconductor light-emitting device 10 according to the presentinvention, FIG. 1 being a plan view and FIG. 2 being a cross sectiontaken along line II—II in FIG. 1.

The semiconductor light-emitting device 10 of the present inventioncomprises a semiconductor substrate 1 having a rear surface providedwith a first electrode 5; a semiconductor layer 3 including alight-emitting portion 2, that is formed on the semiconductor substrate1; dispersed electrodes 7 individually formed on a part of the surfaceof the semiconductor layer 3 to make ohmic contact with thesemiconductor layer 3; a transparent conductive film 4 formed to coverthe surface of the semiconductor layer 3 and the dispersed electrodes 7and electrically conducted with the dispersed electrodes 7; and a padelectrode 6 formed on a part of the surface of the transparentconductive film 4 and electrically conducted with the transparentconductive film 4. As shown in FIG. 1, each of the dispersed electrodes7 is disposed at a position where it does not overlap the pad electrode6 when viewed from the above. It is preferable that each of thedispersed electrodes 7 is not disposed at a position where it overlapsthe pad electrode 6. Furthermore, a junction between the dispersedelectrodes 7 and the semiconductor layer 3 keeps a good ohmic contact tomake an electrical resistance between them small. Another junctionbetween the transparent conductive film 4 and the semiconductor layer 3does not exhibit sufficient ohmic contact. Accordingly, an electricalresistance between them is large.

In the semiconductor light-emitting device 10, the dispersed electrodesare individually provided on a part of the surface of the semiconductorlayer 3 so that they make ohmic contact with the semiconductor layer 3.This configuration enables the electrical resistance between thedispersed electrodes 7 and the semiconductor layer 3 to be much smallerthan that between the transparent conductive film 4 and thesemiconductor layer 3. The major part of a driving current supplied fromthe pad electrode 6 flows through a path from the pad electrode 6 to thesemiconductor layer 3 (the light-emitting portion 2) via the transparentconductive film 4 and the dispersed electrodes 7. This offers a smallerelectrical resistance, as shown by the arrows in FIG. 2. For thisreason, it is possible to allow the light-emitting portion 2 to emitlight at the periphery of the dispersed electrodes 7. Accordingly, thedriving current from the pad electrode 6 can be spread to a wide regionon the surface of the semiconductor layer 3 in accordance with theplanar arrangement of the dispersed electrodes 7. The emitted light canbe taken out from the upper part of the light-emitting device 10 via thetransparent conductive film 4. Since the dispersed electrodes 7 arearranged so that they do not overlap the pad electrode 6 as describedabove, a light emission toward just below the pad electrode 6 does notoccur. A major part of the emitted light is not intercepted by the padelectrode 6 and is taken out from the upper part of the semiconductorlight-emitting device 10, thus improving a light-emitting efficiencysignificantly.

Moreover, since the area of each of the dispersed electrodes 7 is set tobe smaller than that of the pad electrode 6, light can be taken out tothe outside of the semiconductor light-emitting device 10 with a highefficiency compared to conventional semiconductor light-emittingdevices. Thus, the light-emitting efficiency can be increased stillmore.

Since the electrical resistance between the dispersed electrodes 7 andthe semiconductor layer 3 is made smaller owing to the ohmic contactbetween them, as described above, it is possible to suppress an increaseof a forward voltage of the semiconductor light-emitting device 10. Theservice life characteristic can thus be increased.

The transparent conductive film 4 is made of, for example, indium tinoxide (ITO) and possesses a good light transmissivity. Accordingly, thelight emitted from the light-emitting portion 2 is little absorbed evenduring passing through the transparent conductive film 4, and the lightcan be taken out upward from the transparent conductive film 4 with ahigh efficiency.

The pad electrode 6 is subjected to wire-bonding for connecting thesemiconductor light-emitting device 10 to an external electric circuit,and hence needs to have a some area. The emitted light based on thedriving current flowing through a pad electrode in the direction justbelow the pad electrode was intercepted by the pad electrode, and couldnot be taken out to the outside of a conventional semiconductorlight-emitting device. For this reason, a countermeasure such asprovision of an insulating layer between the pad electrode and thelight-emitting portion was taken to forcibly prevent the driving currentfrom flowing from the pad electrode in the direction just below the padelectrode. In the present invention, however, the driving current can beguided to the individual dispersed electrodes 7 not overlapping the padelectrode. Accordingly, without provision of an insulating layer, it ispossible to suppress the driving current flowing in the direction justbelow the pad electrode 6 with a more simplified constitution.

An area on the surface of the transparent conductive film 4 (the surfaceof the semiconductor layer 3 that becomes effective at the time of lightemission is obtained by subtracting the area of the pad electrode 6 fromthe area of the surface of the transparent conductive film 4. This areawill be called an effective light-emitting area S. The phenomenon thatthe pad electrode 6 obstructs takeout of the emitted light from theportion of the pad electrode 6 arises similarly in the dispersedelectrodes 7. Accordingly, in the present invention, the total surfacearea of the dispersed electrodes 7 is set to be in the range of 3% to30% of the effective light-emitting area S. This can eliminate thedisadvantage in that the area of the dispersed electrodes 7 is so widethat takeout of the emitted light is excessively obstructed and thedisadvantage in that the area of the dispersed electrodes 7 is so narrowthat a forward voltage V_(f) is increased.

Various embodiments of the semiconductor light-emitting device accordingto the present invention will be described in detail with reference toFIGS. 3 to 9.

FIGS. 3 and 4 show a first embodiment of the semiconductorlight-emitting device according to the present invention. FIG. 3 is aplan view thereof and FIG. 4 is a cross section taken along line IV—IVin FIG. 3. In these figures, the semiconductor light-emitting device 20of the present invention is a light emitting diode (LED) for emitting areddish-orange light. On a single crystal substrate 21 made of Zn-dopedp-type (001)-GaAs, is formed a semiconductor layer 23 comprising abuffer layer 231 made of Zn-doped p-type GaAs, a lower clad layer 232made of Zn-doped p-type (Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P, alight-emitting layer 22 made of a mixed crystal of undoped n-type(Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P, and an upper clad layer 233 made ofSi-doped n-type (Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P, which aresequentially stacked.

Each of the layers 231, 232, 22 and 233 constituting the semiconductorlayer 23 was grown on the substrate 21 under a reduced pressure by themetal organic chemical vapor deposition (MOCVD), using trimethylaluminum ((CH₃)₃Al), trimethyl gallium ((CH₃)₃Ga) and trimethyl indium(CH₃)₃In) as raw materials for Group-III constituent elements. Diethylzinc ((C₂H)₂Zn) was used as a doping raw material of Zn. Disilane(Si₂H₆) was used as an n-type doping raw material. Moreover, phosphine(PH₃) or arsine (AsH₃) was used as a raw material for Group-Vconstituent elements. The film growth temperature of each of the layers231, 232, 22 and 233 was standardized to 730° C. The carrierconcentration of the buffer layer 231 was set to be about 5×10¹⁸ cm⁻³,and the film thickness thereof was set to be about 0.5 μm. The carrierconcentration of the lower clad layer 232 was set to be about 3×10¹⁸cm⁻³, and the film thickness thereof was set to be about 1 μm. The filmthickness of the light-emitting layer 22 was set to be about 0.5 μm, andthe carrier concentration thereof was set to be about 5×10¹⁶ cm⁻³. Thecarrier concentration of the upper clad layer 233 was set to be about2×10¹⁸ cm⁻³, and the film thickness thereof was set to be about 3 μm.

The lower clad layer 232, light-emitting layer 22 and upper clad layer233 constitute a light-emitting portion of this semiconductorlight-emitting device 20. Therefore, the light-emitting portion is madeof AlGaInP.

In this semiconductor light-emitting device 20, a dispersed electrode 27was formed by first forming a first film 271 of gold-germanium alloy(Au: 93% by weight+Ge: 7% by weight) having a thickness of about 50 nmon the entire surface of the upper clad layer 233 using a general vacuumdeposition method, subsequently forming a second film 272 of Au having athickness of about 50 nm on the surface of the first film, and usinggeneral photolithography means to pattern the two-film layer structureso that the two-film layer structure (dispersed electrode 27) wassquare-shaped with a side of about 20 μm. As shown in FIG, 3, twelvedispersed electrodes 27 each composed of the first film 271 and thesecond film 272 were provided so that they were symmetrically arrangedon the surface of the upper clad layer 233 at positions other than theposition just below a pad electrode 26. A distance L between the centersof the adjacent dispersed electrodes 27 was set to be 50 μm. After thedispersed electrodes 27 were formed on the surface of the upper cladlayer 233, a heat treatment for alloying was performed for 15 minutes at420° C. in the stream of Ar gas, thus forming ohmic contact between thedispersed electrodes 27 and the upper clad layer 233.

The upper clad layer 233 and the dispersed electrodes 27 on the surfaceof the upper clad layer 233 are covered by a transparent conductive film24 that is made of indium tin oxide (ITO) by a general magnetronsputtering method. The specific resistance of the transparent conductivefilm 24 was about 4×10⁻⁴ Ω·cm, and the thickness thereof was set to beabout 600 nm. By a general X-ray diffraction analysis, the transparentconductive film 24 was found to be a polycrystalline film in which it ispreferentially oriented to the direction of <0001>(C-axis).

An ordinary organic photoresist material was coated on the entiresurface of the transparent conductive film 24 and then patternedutilizing a known photolithography technique to have a region where thepad electrode 26 is to be provided.

The region is set to include the center of the surface of thesemiconductor light-emitting device shown in FIG. 3 (the intersection ofthe diagonals of a square). This is because the distance between theregion and the individual dispersed electrodes 27 is made uniform toallow a current to uniformly flow through the dispersed electrodes 27and through the whole of the semiconductor light-emitting device. Afurther reason is that the inclination of the semiconductor chip thatwould be formed during the wire-bonding process if the region shoulddeviate greatly from the center can be prevented.

Thereafter, an Au film was formed by a vacuum deposition method on theentire surface of the patterned photoresist material. The thickness ofthe Au film was set to be about 700 nm. Thereafter, accompanied withpeeling off the photoresist material, the Au film was formed by awell-known lift-off means so that it was laid restrictedly on the regionwhere the pad electrode 26 is to be formed. Thus, the circular padelectrode 26 of Au having a diameter of about 110 μm was formed. Thearea of the pad electrode 26 was about 0.95×10⁻⁴ cm².

On the other hand, a p-type ohmic electrode 25 of Au—Zn alloy was formedon the rear surface of the single crystal substrate 21. Thesemiconductor light-emitting device 20 thus fabricated was in the shapeof a square having a side of 260 μm, so that the area of the transparentconductive film 24 was about 6.8×10⁻⁴ cm². The effective light-emittingarea S obtained by subtracting the area of the pad electrode 26 from thearea of the transparent conductive film 24 was about 5.9×10⁻⁴ cm².Moreover, the total area of the dispersed electrodes 27 was 0.48×10⁻⁴cm², and the ratio of this total area to the effective light-emittingarea S was about 8.1%.

When a current flowed in the forward direction between the p-type ohmicelectrode 25 and the pad electrode 26 of the semiconductorlight-emitting device 20 fabricated in this manner, reddish-orange lighthaving a wavelength of about 620 nm was emitted from the surface of thetransparent conductive film 24. As a result of measurement by amonochrometer, a half bandwidth of the emission spectrum was about 20nm, and a light emission excellent in monochromaticity was obtained.Reflecting a good ohmic characteristic of each dispersed electrode 27, aforward voltage (V_(f)) per 20 mA when a current of 20 mA flowed wasabout 2.1 V. By virtue of the effect obtained by arranging the ohmicdispersed electrodes 27 at the peripheral region within the square ofthe semiconductor light-emitting device 20, a light emission wasrecognized also at the peripheral region. In the state where a visualsensitivity of the semiconductor light-emitting device 20 in the form ofa chip was corrected utilizing a commercially available integratingsphere, the intensity of the emitted light simply measured was about 42mcd. Moreover, since the driving current was uniformly applied to theindividual dispersed electrodes 27, the distribution of the lightemission intensity observed on the surface of the transparent conductivefilm 24 was substantially uniform.

Comparative Example

A sample semiconductor light-emitting device (LED) was fabricated in thesame manner as in the first embodiment for comparison with thesemiconductor light-emitting device 20 in the first embodiment. However,this sample device was provided with an ohmic electrode having the sameshape as the pad electrode 26 of the first embodiment. The ohmicelectrode comprised a lower layer of Au—Ge alloy 50 nm in thickness thatwas formed directly on the surface of the upper clad layer 233 and anupper layer made of Au 50 nm in thickness. Therefore, the sample devicedid not have either the transparent conductive film 24 or the dispersedelectrode 27.

The V_(f) value (per 20 mA) of the sample device was about 2V, which wasapproximately equal to the V_(f) value of the semiconductorlight-emitting device 20 of the first embodiment. In the sample device,since the flat ohmic electrode having the total thickness of about 100nm was provided directly on the upper clad layer 233, the light emissionoccurred only just below and around the ohmic electrode. A large amountof the emitted light was intercepted by the electrode and could not betaken out. As a result, the light emission intensity of the sampledevice was at a low level of about 20 mcd.

The semiconductor light-emitting device 20 of the first embodiment has astructure in which the ohmic dispersed electrodes 27 whose area ofcontact with the semiconductor layer 23 (the upper clad layer 233) issmall are disposed without reducing the effective light-emitting area Sand increasing the V_(f) value. It is apparent that this structureenables high luminance to be realized.

FIGS. 5 and 6 show a second embodiment of the semiconductorlight-emitting device according to the present invention. FIG. 5 is aplan view of thereof and FIG. 6 is a cross section taken along lineVI—VI in FIG. 5. In these figures, the semiconductor light-emittingdevice 30 is a light emitting diode (LED) which emits reddish-orangelight. The semiconductor light-emitting device 30 is constituted bysequentially stacking on a single crystal substrate 31 of Si-dopedn-type (001) 2°-off GaAs, a buffer layer 331 of Si-doped n-type GaAs, aBragg reflection (DBR) layer 332 of a periodic structure in which 10Si-doped n-type Al_(0.40)Ga_(0.60)As layers and 10 n-typeAl_(0.95)Ga_(0.05)As layers are alternately stacked periodically, alower clad layer 333 of Si-doped n-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P, a light-emitting layer 32 made of amixed crystal of undoped n-type (Al_(0.2)Ga_(0.8))_(0.5)In_(0.5)P, andan upper clad layer 334 of Mg-doped p-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P by a reduced-pressure MOCVD method.The foregoing layers 331, 332, 333, 32 and 334 constitute asemiconductor layer 33.

Each of the layers 331, 332, 333, 32 and 334 constituting thesemiconductor layer 33 was grown by the reduced-pressure MOCVD method,using trimethyl aluminum ((CH₃)₃Al), trimethyl gallium ((CH₃)₃Ga) andtrimethyl indium (CH₃)₃In) as raw materials for Group-III constituentelements and using phosphine (PH₃) or arsine (AsH₃) as a raw materialfor Group-V constituent elements. Bis-cyclopentadienyl magnesium(bis-(C₅H₅)₂Mg) was used as a doping raw material of Mg. Disilane(Si₂H₆) was used as an n-type doping raw material. The film growthtemperature of each of the layers 331, 332, 333, 32 and 334 wasstandardized to 730° C. The carrier concentration of the buffer layer331 was set to be about 3×10¹⁸ cm⁻³, and the thickness thereof was setto be about 500 nm. The thickness of each of the n-typeAl_(0.40)Ga_(0.60)As layers and the n-type Al_(0.95)Ga_(0.05)As layerswhich constitute the DBR layer, was set to be about 40 nm. The carrierconcentration of the lower clad layer 333 was set to be about 3×10¹⁸cm⁻³, and the thickness thereof was set to be about 400 nm. Thethickness of the light-emitting layer 32 was set to be about 10 nm, andthe carrier concentration thereof was set to be about 1×10¹⁷ cm⁻³. Thecarrier concentration of the upper clad layer 334 was set to be about4×10¹⁸ cm⁻³, and the thickness thereof was set to about 3 μm.

A film of Ni having a thickness of about 15 nm was coated on the entiresurface of the upper clad layer 334 by a general electron beam vacuumdeposition method The Ni film was then patterned utilizing a generalphotolithography means, thus forming eight circular dispersed electrodes37 each having a diameter of 20 μm on the upper clad layer 334. Thedispersed electrodes 37 were disposed at regular intervals on a circlehaving a radius R of 95 μm from the center of a pad electrode 36 and onthe diagonals on the surface of the upper clad layer 334 as well asbetween the diagonals, other than the region just below the padelectrode 36. After the dispersed electrodes 37 were formed, a heattreatment for alloying was performed, thus forming ohmic contact betweenthe dispersed electrodes 37 and the upper clad layer 334.

After the dispersed electrodes 37 were formed on the upper clad layer334, a film of indium tin oxide (ITO) was deposited on the upper cladlayer 334 and the dispersed electrodes 37 as a transparent conductivefilm 34 by a general magnetron sputtering method. The specificresistance of the transparent film 34 was set to be about 4×10⁻⁴ Ω·cm,and the thickness thereof was set to be about 600 nm. By a general X-raydiffraction analysis, the transparent conductive film 34 was found to bea polycrystalline film in which it is preferentially oriented to thedirection of <0001>(C-axis). The transparent conductive film 34 wasgrown at a temperature of 250° C.

An ordinary organic photoresist material was coated on the entiresurface of the transparent conductive film 34 and then a region wherethe pad electrode 36 is to be provided was patterned utilizing a knownphotolithography technique. Thereafter, a Ti film was formed on theentire surface of the patterned photoresist material by an electron beamvacuum deposition method. The thickness of the Ti film was set to beabout 600 nm. Thereafter, accompanied with peeling off the photoresistmaterial, the Ti film was laid by a well-known lift-off meansrestrictedly on the region where the pad electrode 36 is to be formed.Thus, the circular pad electrode 36 of Ti having a diameter of about 120μm was formed on the transparent conductive film 34. The area of the padelectrode 36 was about 1.1×10⁻⁴ cm².

An n-type ohmic electrode 35 of Au—Ge alloy was formed on a rear surfaceof the single crystal substrate 31. The semiconductor light-emittingdevice 30 thus fabricated was in the shape of a square having a side of260 μm, so that the area of the transparent conductive film 34 becameabout 6.8×10⁻⁴ cm². The effective light-emitting area S obtained bysubtracting the area of the pad electrode 36 from the area of thetransparent conductive film 34 was about 5.7×10⁻⁴ cm². Moreover, thetotal area of the dispersed electrodes 37 was 0.25×10⁻⁴ cm², and theratio of this total area to the effective light-emitting area S wasabout 4.4%.

When current flowed in the forward direction between the n-type ohmicelectrode 35 and the pad electrode 36, reddish-orange light having awavelength of about 620 nm was emitted from the surface of thetransparent conductive film 34. As a result of measurement by amonochrometer, a half bandwidth of the emission spectrum was about 20nm, and a light emission excellent in monochromaticity was obtained.Reflecting a good ohmic characteristic of each dispersed electrode 37, aforward direction voltage (V_(f)) per 20 mA when a current of 20 mAflowed was about 2.1 V. By virtue of the effect obtained by arrangingthe ohmic dispersed electrodes 37 at the peripheral region within thesquare of the semiconductor light-emitting device 30, a light emissionwas recognized also at the peripheral region. In the state where avisual sensitivity of the semiconductor light-emitting device 30 in theform of a chip was corrected utilizing a commercially availableintegrating sphere, the intensity of the emitted light simply measuredwas about 74 mcd. Moreover, since the driving current was uniformlyapplied to the individual dispersed electrodes 37, the distribution ofthe light emission intensity observed on the surface of the transparentconductive film 34 was substantially uniform. The semiconductorlight-emitting device 30 of the second embodiment also has a structure mwhich the ohmic dispersed electrodes 37 whose area of contact with thesemiconductor layer 33 (the upper clad layer 233) is small are disposedwithout reducing the effective light-emitting area S and increasing theV_(f) value. It is apparent that this structure enables high luminanceto be realized.

FIGS. 7 and 8 show a third embodiment of the semiconductorlight-emitting device according to the present invention. FIG. 7 is aplan view thereof and FIG. 8 is a cross section taken along lineVIII—VIII in FIG. 7. In these figures, the semiconductor light-emittingdevice 40 is a light emitting diode (LED) which emits yellowish-greenlight. The semiconductor light-emitting device 40 comprises a singlecrystal substrate 41 of Zn-doped p-type (001) 4°-off GaAs and asemiconductor layer 43 formed on the substrate. The semiconductor layer43 comprises a buffer layer 431 of Zn-doped p-type GaAs, a Braggreflection (DBR) layer 432 of a structure in which 12 Al_(0.4)Ga_(0.6)Aslayers and 12 Al_(0.9)Ga_(0.1)As layers are alternately stacked, a lowerclad layer 433 of Zn-doped p-type Al_(0.5)In_(0.5)P, a light-emittinglayer 42 made of a mixed crystal of undoped(Al_(0.4)Ga_(0.6))_(0.5)In_(0.5)P, an upper clad layer 434 made of amixed crystal of Se-doped n-type Al_(0.5)In_(0.5)P, and a contact layer435 made of a mixed crystal of Se-doped n-type(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P, that are sequentially formed on thesubstrate 41.

Each of the layers 431, 432, 433, 42, 434 and 435 constituting thesemiconductor layer 43 was grown by the reduced-pressure MOCVD method,using trimethyl aluminium ((CH₃)₃Al), trimethyl gallium ((CH₃)₃Ga) andtrimethyl indium (CH₃)₃In) as raw materials for Group-III constituentelements and using phosphine (PH₃) or arsine (AsH₃) as a raw materialfor Group-V constituent elements. Diethyl zinc ((C₂H₅)₂Zn) was used as adoping raw material of Zn. Hydrogen selenide (H₂Se) was used as ann-type doping raw material. The film growth temperature of each of thelayers 431, 432, 433, 42, 434 and 435 was standardized to 730° C. Thecarrier concentration of the buffer layer 431 was set to be about 5×10¹⁸cm⁻³, and the thickness thereof was set to be about 0.5 μm. The carrierconcentration of the DBR layer 432 was set to be about 1×10¹⁸ cm⁻³, andthe thickness was set to be about 1 μm. The carrier concentration of thelower clad layer 433 was set to be about 3×10¹⁷ cm⁻³, and the thicknessthereof was set to be about 1.5 μm. The thickness of the light-emittinglayer 42 was set to be about 0.8 μm, and the carrier concentrationthereof was set to be about 5×10¹⁶ cm⁻³. The carrier concentration ofthe upper clad layer 434 was set to be about 1×10¹⁸ cm⁻³, and thethickness thereof was set to about 5 μm. The carrier concentration ofthe contact layer 435 was set to be about 2×10¹⁸ cm⁻³, and the thicknessthereof was set to about 0.5 μm.

The lower clad layer 433, light-emitting layer 42 and upper clad layer434 constitute a light-emitting portion of this semiconductorlight-emitting device 40. Therefore, the light-emitting portion is madeof AlGaInP.

In this semiconductor light-emitting device 40, a dispersed electrode 47was formed by first forming a first film 471 of gold-germanium alloy(Au: 93% by weight+Ge: 7% by weight) having a thickness of about 50 nmon the entire surface of the contact layer 435 using a general vacuumdeposition method, subsequently forming a second film 272 of Au having athickness of about 50 nm on the surface of the first film 471, and usinggeneral photolithography means to pattern the two-film layer structureso that the two-film layer structure (dispersed electrode 47) wascircle-shaped with a diameter of about 20 μm. On the surface of thesingle crystal substrate 41 of GaAs opposite the surface thereof onwhich the semiconductor layer 43 was formed, a 150 nm-thick film ofAu—Be alloy and a 800 nm-thick film of Au were vacuum-deposited to forma p-type ohmic electrode 45. As shown in FIG, 7, twelve dispersedelectrodes 47 each composed of the first film 471 and the second film472 were provided so that they were arranged on the surface of thecontact layer 435 at positions other than the position just below a padelectrode 46. The distance L between the centers of the adjacentdispersed electrodes 47 was set to be 50 μm. A heat treatment foralloying was performed for 15 minutes at 420° C. in the stream of Argas, thus forming ohmic contact between the dispersed electrodes 47 andthe contact layer 435 and between the single crystal substrate 41 ofGaAs and the p-type ohmic electrode 45.

The contact layer 435 and the dispersed electrodes 47 were covered by atransparent conductive film 44 that was made of indium tin oxide (ITO)by a general magnetron sputtering method. The specific resistance of thetransparent conductive film 44 was about 4×10⁻⁴ Ω·cm, the transmissivityof visible light thereto was about 95%, and the thickness thereof wasset to be about 300 nm. By a general X-ray diffraction analysis, thetransparent conductive film 44 was found to be a polycrystalline film inwhich it is preferentially oriented to the direction of <0001>(C-axis).

A Cr film 461 and an Au film 462 were deposited on the entire surface ofthe transparent conductive film 44 by the sputtering method. Thethickness of the Cr film 461 was 50 nm and that of the Au film was about3000 nm.

An ordinary organic photoresist material was coated on the entiresurface of the transparent conductive film 44 on which the Cr and Aufilms were deposited and then patterned utilizing a knownphotolithography technique to have a region where the pad electrode 26is to be provided.

Thereafter, the Cr film 461 and Au film 462 in the region other than thepatterned region were removed by etching. The photoresist material wasthen peeled off to obtain a circular pad electrode 46 consisting of theCr film and Au film and having a diameter of about 110 μm was formed.The area of the pad electrode 46 was about 0.95×10⁻⁴ cm².

The semiconductor light-emitting device 40 thus fabricated was in theshape of a square having a side of 260 μm, so that the area of thetransparent conductive film 44 was about 6.8×10⁻⁴ cm². The effectivelight-emitting area S obtained by subtracting the area of the padelectrode 46 from the area of the transparent conductive film 44 wasabout 5.9×10⁻⁴ cm². Moreover, the total area of the dispersed electrodes47 was 0.38×10⁻⁴ cm², and the ratio of this total area to the effectivelight-emitting area S was about 6.4%.

When a current flowed in the forward direction between the p-type ohmicelectrode 45 and the pad electrode 46 of the semiconductorlight-emitting device 40 fabricated in this manner, yellowish-greenlight having a wavelength of about 573 nm was emitted from the surfaceof the transparent conductive film 44. Thus, an excellent light emissionwas obtained. Reflecting a good ohmic characteristic of each dispersedelectrode 47, a forward voltage (V_(f)) per 20 mA when a current of 20mA flowed was about 2.1 V. By virtue of the effect obtained by arrangingthe ohmic dispersed electrodes 47 at the peripheral region within thesquare of the semiconductor light-emitting device 40, a light emissionwas recognized also at the peripheral region. In the state where avisual sensitivity of the semiconductor light-emitting device 40 in theform of a chip was corrected utilizing a commercially availableintegrating sphere, the intensity of the emitted light simply measuredwas about 38 mcd. Moreover, since the driving current was uniformlyapplied to the individual dispersed electrodes 47, the distribution ofthe light emission intensity observed on the surface of the transparentconductive film 44 was substantially uniform.

FIGS. 9(a) to 9(y) are plan views showing examples of the arrangement ofthe dispersed electrodes. In the foregoing embodiments, the dispersedelectrodes 7 (27, 37, 47) are disposed around the pad electrode 6 (26,36, 46) so that they are individually scattered and do not overlap thepad electrode 6. However, they may be continuously connected and, ifnecessary, may be disposed in a state overlapping the pad electrode 6(26, 36, 46). In FIGS. 9(a) to 9(y), the pad electrode 6 and dispersedelectrode 7 are given reference symbols “a” to “y” corresponding tothese figures, added to each of reference numerals 6 and 7. For example,the pad electrode and dispersed electrode in FIG. 9(a) are givenreference symbols 6 a and 7 a, respectively. Each of the transparentconductive layers also given similar reference symbols 4 a to 4 r isformed to cover the dispersed electrode and the surface of thesemiconductor layer (not shown).

The dispersed electrode 7 a in FIG. 9(a) comprises a band-shapedrectangular frame body 71 a that surrounds the pad electrode 6 a, andbranches 71 b abundantly distributed perpendicular to the frame body 71a. The dispersed electrode 7 b in FIG. 9(b) comprises two band-shapebodies 71 b arranged on the opposite sides of the pad electrode 6 b anda connection body 72 b which passes through just below the pad electrode6 b to connect the two band-shaped bodies 71 b. The dispersed electrode7 c in FIG. 9(c) comprises two rectangular flat bodies 7 c disposed onthe opposite sides of the pad electrode 6 c. The dispersed electrode 7 din FIG. 9(d) comprises a band-shaped rectangular frame body 71 d thatsurrounds the pad electrode 6 d and four band-shaped bodies 72 dextending in the radial direction from the corners of the frame body 71d The dispersed electrode 7 e in FIG. 9(e) comprises a honeycomb-shapedbody 7 e disposed on the entire surface or semiconductor layer (notshown) including a region just below the pad electrode 6 e.

In FIG. 9(f) there are four polygonal dispersed electrodes 7 f (regularhexagon) disposed around the square-shaped pad electrode 6 f at the foursides thereof. The dispersed electrode 7 g in FIG. 9(g) comprises fourband-shaped bodies 7 g disposed on the diagonals of the square-shapedsurface of the semiconductor layer (not shown). In FIG. 9(h) thedispersed electrode 7 h comprises a lattice band-shaped body, with apart thereof corresponding to the region of the pad electrode 6 hremoved. The dispersed electrode 7 i in FIG. 9(i) comprises a pluralityof slender band-shaped bodies extending in the radial direction, withthe pad electrode 6 i as the center. The dispersed electrode 7 j in FIG.9(j) is a frame body surrounding the pad electrode 6 j. The dispersedelectrode 7 k in FIG. 9(k) comprises an annular body 71 k surroundingthe pad electrode 6 k and four square bodies 72 k disposed on thediagonals of the square surface of the semiconductor layer (not shown).The dispersed electrode 7 l in FIG. 9(l) comprises two annular bodies 71l and 72 l disposed concentrically relative to the circular padelectrode 6 l. The dispersed electrode 7 m in FIG. 9(m) comprises twopairs of crescent-shaped bodies, each pair disposed on the circumferenceof a circle concentric with the pad electrode 6 m. The dispersedelectrode 7 n in FIG. 9(n) comprises an annular body 71 n surroundingthe pad electrode 6 n and four crescent-shaped bodies 72 n disposed onthe circumference of a circle concentric with the pad electrode 6 n. Thedispersed electrode 7 o in FIG. 9(o) comprises a hexagonal frame body 71o surrounding the hexagonal pad electrode 6 o and branches 72 oextending outward from the frame body 71 o. The dispersed electrode 7 pin FIG. 9(p) comprises four arcuate bodies disposed on the circumferenceof a circle concentric with the pad electrode 6 p and four arcuatebodies disposed on the circumference of a larger concentric circle. Thedispersed electrode 7 q in FIG. 9(q) comprises a plurality ofband-shaped bodies connected to form a polygonal shape that can surroundthe polygonal pad electrode 6 q. The dispersed electrode 7 r in FIG.9(r) comprises four band-shaped hooks 71 r each bent at right angles anddisposed on the diagonals of the square surface of the semiconductorlayer (not shown) and branches 72 r extending outward in the radialdirection from the corners of the hooks 71 r.

In FIGS. 9(s) to 9(y), the dispersed electrode is a metal film formed onthe entire surface of the semiconductor layer (not shown), but removedat a position corresponding to the position of the pad electrode, andformed with holes. With this configuration, a light emission interceptedby the pad electrode is prevented from being induced in thesemiconductor layer. The holes and remaining metal film (dispersedelectrode) are covered by the transparent conductive layer (not shown),and the light emission induced in the semiconductor layer in thepresence of the dispersed electrode is taken out via the holes andtransparent conductive layer. The holes are given reference symbols “g”to “y” corresponding to these figures, added to each of referencenumerals 9.

The dispersed electrode 7 s in FIG. 9(s) is the metal film having aplurality of square holes 9 s arranged in the peripheral region withinthe square surface of the semiconductor layer (not shown). The dispersedelectrode 7 t in FIG. 9(t) is the metal film having a great number ofcircular holes 9 t arranged in the lateral and longitudinal directionswithin the square surface of the semiconductor layer (not shown). Thedispersed electrode 7 u in FIG. 9(u) is the metal film having aplurality of polygonal holes 9 s arranged in the peripheral regionwithin the square surface of the semiconductor layer (not shown). Thedispersed electrode 7 v in FIG. 9(v) is the metal film having aplurality of holes 9 v consisting of circular holes 91 v arranged in theperipheral region within the square surface of the semiconductor layer(not shown) and polygonal holes 92 v disposed inside the circular holes91 v. The dispersed electrode 7 w in FIG. 9(w) is the metal film havinga plurality of band-shaped holes 9 w arranged in the lateral andlongitudinal directions within the square surface of the semiconductorlayer (not shown). The dispersed electrode 7 x in FIG. 9(x) is the metalfilm having a plurality of substantially H-shaped holes 9 x arranged inthe peripheral region within the square surface of the semiconductorlayer (not shown). The dispersed electrode 7 y in FIG. 9(y) is the metalfilm having a plurality of rectangular holes 9 y arranged in theperipheral region within the square surface of the semiconductor layer(not shown).

As described above, the dispersed electrode includes individuallydispersed ones, a band-shaped integral one, planar ones and a planarintegral one with a plurality of holes.

When the dispersed electrodes are individually disposed, they may be inthe shape of a square, a rectangle, a circle singly or in combination orin any other shape and also in a pattern that is radial, circular,spiral or in any other pattern. Further, in FIGS. 9(a) to 9(y), thetransparent conductive film is given reference symbols “a” to “y”corresponding to these figures, added to reference numeral 4.

An LED lamp 80 fabricated using the semiconductor light-emitting deviceaccording to the present invention will be described.

FIG. 10 is a schematic view showing the LED lamp that comprises asemiconductor light-emitting device 81, a mount lead 82, an inner lead83 and a molding of transparent resin 84.

The semiconductor light-emitting device 20 in the first embodiment or 30in the second embodiment is used as the device 81. An electrode 81 a(the p-type ohmic electrode 25 in the first embodiment or n-type one 35in the second embodiment) is fixed onto the mount lead 82 to formelectrical contact with the mount lead 82. A pad electrode 81 b (the padelectrode 26 in the first embodiment or 36 in the second embodiment) isbonded to the inner lead 83 by wire-bonding.

In the conventional semiconductor light-emitting device disclosed inJP-A SHO 57(1982)-111076, a transparent conductive layer is formed tocover a pad electrode. With this configuration, since the conductivelayer is transparent, it is difficult to recognize the region of thetransparent conductive layer. As a result, there is a possibility of thesurface of the transparent conductive layer is subjected towire-bonding, resulting in a state of a wire not adhering to the padelectrode. In the present invention, however, such inconvenience can beeliminated because no transparent conductive layer exists on the surfaceof the pad electrode subjected to wire-bonding.

Since the LED lamp 80 has the semiconductor light-emitting device of thepresent invention, the light-emitting efficiency thereof is higher thana conventional one, and the service life characteristic thereof isenhanced.

Furthermore, the LED lamp 80 can be used as a lighting implement forvehicles, railway rolling stock, traffic signals, railroad crossingsignals, road-shoulder pilot lamps and eye guide lamps. It can also beused as a light source for monitor indicators, operation plateindicators, office machines including duplicators and facsimilemachines, information panels used outdoors, etc. In this case, the lightsource using the LED lamp 80 of the present invention exhibits a higherlight-emitting efficiency and a more enhanced service lifecharacteristic than a conventional one.

As has been described in the foregoing, in the semiconductorlight-emitting device of the present invention, dispersed electrodes areindividually provided on a part of the surface of a semiconductor layerso that they make ohmic contact with the semiconductor layer. Thisconfiguration enables the electrical resistance between the dispersedelectrodes and the semiconductor layer to be much smaller than thatbetween a transparent conductive film and the semiconductor layer. Themajor part of a driving current supplied from a pad electrode flowssuccessively to a transparent conductive film, the dispersed electrodesand the semiconductor layer (light-emitting portion) in the directionoffering lower electrical resistance. Therefore, light emission from thelight-emitting portion can be performed around the dispersed electrodes.Moreover, since almost all of the dispersed electrodes are disposed soas not to overlap the pad electrode, light emission toward just belowthe pad electrode does not occur. Accordingly, the major part of theemitted light is not intercepted by the pad electrode and can be takenout from the upper portion of the semiconductor light-emitting device,thus improving the light-emitting efficiency to a great extent.Furthermore, since the area of the dispersed electrodes is set to besmaller than that of the pad electrode, light can be taken out to theoutside with a better light-emitting efficiency than that of aconventional light-emitting device.

In addition, since the electrical resistance between the dispersedelectrodes and the semiconductor layer becomes smaller, it is possibleto reduce the forward current of the semiconductor light-emittingdevice, thus enhancing the service life characteristic of the device.

Moreover, the transparent conductive film exhibits a goodtransmissivity, so that the light from the light-emitting portion islittle absorbed during passing through the transparent conductive filmand can be taken out upward from the transparent conductive film with ahigh efficiency.

The light emitted based on the driving current from the pad electrodeflowing in the direction just below the pad electrode is intercepted bythe pad electrode, resulting in waste of power consumption. For thisreason, the countermeasure such as provision of an insulating layerbetween the pad electrodes and the light-emitting portion has been takento forcibly prevent the driving current from flowing from the padelectrode to the direction just below the pad electrode. In the presentinvention, the driving current can be guided to the dispersed electrodesusing a simplified constitution that can prevent the driving currentfrom flowing to the direction just below the pad electrode without usingan insulating layer.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. A semiconductor light-emitting device comprising:a semiconductor substrate having a rear surface on which a firstelectrode is formed; a semiconductor layer including a light-emittingportion, that is formed on said semiconductor substrate; dispersedelectrodes individually formed on a part of a surface of saidsemiconductor layer, said dispersed electrodes making ohmic contact withsaid semiconductor layer; dispersed electrodes individually formed on apart of a surface of said semiconductor layer, said dispersed electrodesmaking ohmic contact with said semiconductor layer; a transparentconductive film formed so as to cover the surface of said semiconductorlayer and said dispersed electrodes, said transparent conductive filmelectrically conducting with said dispersed electrodes; and a padelectrode formed on a part of a surface of said transparent conductivefilm, said pad electrode electrically conducting with the transparentconductive film, wherein said dispersed electrodes have a total planearea smaller than a plane area of said pad electrode.
 2. A semiconductorlight-emitting device comprising: a semiconductor substrate having arear surface on which a first electrode is formed; a semiconductor layerincluding a light-emitting portion, that is formed on said semiconductorsubstrate; dispersed electrodes individually formed on a part of asurface of said semiconductor layer, said dispersed electrodes makingohmic contact with said semiconductor layer; a transparent conductivefilm formed so as to cover the surface of said semiconductor layer andsaid dispersed electrodes, said transparent conductive film electricallyconducting with said dispersed electrodes; and a pad electrode formed ona part of a surface of said transparent conductive film, said padelectrode electrically conducting with the transparent conductive film,wherein said dispersed electrodes have a total plane area in a range of3% to 30% of an effective light-emitting area.
 3. An electrode for asemiconductor light-emitting device comprising: dispersed electrodesformed on a part of a surface of a semiconductor layer including alight-emitting portion to make ohmic contact with said semiconductorlayer; a transparent conductive film formed to cover the surface of saidsemiconductor layer and said dispersed electrodes to electricallyconduct with said dispersed electrodes; and a pad electrode formed on apart of a surface of said transparent conductive film to electricallyconduct with said transparent conductive film, wherein said dispersedelectrodes have a total plane area smaller than a plane area of said padelectrode.
 4. An electrode for a semiconductor light-emitting devicecomprising: dispersed electrodes formed on a part of a surface of asemiconductor layer including a light-emitting portion to make ohmiccontact with said semiconductor layer; a transparent conductive filmformed to cover the surface of said semiconductor layer and saiddispersed electrodes to electrically conduct with said dispersedelectrodes; and a pad electrode formed on a part of a surface of saidtransparent conductive film to electrically conduct with saidtransparent conductive film, wherein said dispersed electrodes have atotal plane area in a range of 3 to 30% of an effective light-emittingarea.